To better understand the origin of NEAs and meteorites
from the dynamical viewpoint, we have studied by numerical
integrations the evolutions of several thousand
fictitous particles originally placed in the main resonances of
the asteroid belt. We have found that the global picture of their
evolution is significantly different in many respects from that
usually discussed in the literature.
This is due to the fact that the main resonances in the asteroid belt
are very efficient in pumping the eccentricities of the resonant
bodies to Sun-grazing values.
The dynamical timescales are very short: half of the particles
`die' in only about 2 Myr, most of them colliding with the Sun.
This was first understood a few years ago
(Farinella et al, Nature 371, 315),
but here we show with the first large
scale simulations how this phenomenon dominates the dynamical
evolution of most objects on Earth-crossing orbits.
This new qualitative picture of how orbits coming out of the
asteroid belt evolve requires a complete re-assessment of models
of NEA and meteorite production.